Comet Labs WN591 Bedienungsanleitung PDF herunterladen (Seite 19)

Help! There is a comet in my computer! 16

Table 1. Subtraction of the background signal for each pixel column of the comet on the model

comet image. The data are for box segmentation (see Figure 8 for grey values of individual pixels).

The pixel column number eight, which is used as an example in the text, is shown in blue numbers.

The background-corrected comet intensity is used for all further calculations. The cumulative comet

intensity is calculated from the background-corrected intensities (a separate cumulative frequency

for the head and the tail).

ROI Number of

pixel

column

Recorded

comet

intensity

(sum of 11

pixels)

Recorded

background

intensity

(sum of 4

pixels)

Average

background

intensity

(per pixel)

Scaled

background

intensity

(for 11 pixels)

Background-

corrected

comet

intensity

(sum of 11

pixels)

Cumulative

comet

intensity

Head 1 1010 169 42 465 545 545

2 1801 174 44 479 1323 1868

3 2165 164 41 451 1714 3582

4 2215 164 41 451 1764 5346

5 2593 164 41 451 2142 7488

6 2646 164 41 451 2195 9683

7 2604 164 41 451 2153 11836

8 2443 169 42 465 1978 13814

9 2336 164 41 451 1885 15699

10 2213 169 42 465 1748 17447

11 1877 164 41 451 1426 18873

Tail

12 1476 169 42 465 1011 1011

13 1439 169 42 465 974 1986

14 1471 164 41 451 1020 3006

15 1379 169 42 465 914 3920

16 1440 164 41 451 989 4909

17 1349 164 41 451 898 5807

18 1349 179 45 492 857 6664

19 1310 164 41 451 859 7523

20 1149 179 45 492 657 8179

21 1210 164 41 451 759 8938

22 1150 169 42 465 685 9624

23 1062 164 41 451 611 10235

24 929 164 41 451 478 10713

25 658 164 41 451 207 10920

Subtraction of the background signal seems to be an easy task. However, the problem is

that the background signal is not completely even across the image - we have some lighter

and some darker pixels. So how can we know whether to subtract 41 or 51 from the grey

value for each individual pixel in the comet? Because we cannot know this, we will

average the background and then subtract it from the comet image.

Now we need to decide which part of the image we will take as the background. One

approach is to take a narrow rectangular region of image just above the comet (Figure 8,

region inside the yellow box). In our case, the height of the background region is 4 pixels.

1 2 ... 14 15 16 17 18 19 20 21 22 23 24 ... 48 49

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